HU176191B - Method for producing aluminium-silicon alloys by carbothermal process - Google Patents

Abstract

Aluminum-silicon alloys are formed by bringing a mix containing sources of alumina, silica and carbon to a temperature in the range of 1500 to 1600.degree.C to form silicon carbide and carbon monoxide. The mix containing the silicon carbide is then brought to a temperature in the range of 1600 to 1900.degree.C to form aluminum oxycarbide and carbon monoxide. Thereafter, the mix containing the silicon carbide and aluminum oxycarbide is brought to a temperature in the range of 1950 to 2200.degree.C to produce an aluminumsilicon alloy.

Description

A process for the production of aluminum-silicon alloys by a carbothermic route

The present invention relates to a process for the preparation of aluminum-silicon alloys from alumina and silica-containing materials by carbothermic processes.

Conventionally, aluminum silicon alloys are prepared by making commercially pure aluminum from hoqjy bauxite alumina in an electrolytic cell and then adding relatively pure silicon to the aluminum produced immediately prior to addition. The process is relatively expensive due to the relatively large number of production steps.

It is known in the art that aluminum-silicon alloys can be prepared from minerals containing alumina and silica in blast furnaces. U.S. Patent No. 5,661,551 discloses a process for the production of aluminum-silicon alloys in blast furnaces. Carbon, alumina-silica ores and pure oxygen are used for production. According to the process described in the patent, hot oxygen is reacted with carbon to form carbon monoxide gas and allows the temperature in the furnace reaction zone to be above 2050 ° C. U.S. Patent No. 5,661,562 discloses a process for producing aluminum silicon alloys in a blast furnace having two reaction zones. In this process, hot carbon monoxide gas formed from carbon and oxygen in the first zone is introduced into a second zone, which is alumina176101

contains silicon ore containing uxiu. The hot s2enic mono-gases passing through the second reaction zone provide the heat needed to produce the aluminum-silicon alloys. U.S. Patent No. 5-758.269 discloses a two-step process for the production of aluminum silicon alloys from alumina-containing ores. In the first step, the silica in the ore is reduced to a product containing silicon carbide. In this process, the product formed in the first step is fed to and heated in an electric furnace where the silicon carbide is converted into elemental silicon and the alumina is converted into aluminum. In these processes, the gases formed are led down the reduction steps, which results in a significant loss of product due to the rapid passage of the gases.

The process of the present invention essentially eliminates the problem of product loss in the production of aluminum silicon alloys from ores containing alumina and silica due to the control of reaction steps.

According to the present invention, aluminum-silicon alloys are prepared by heating alumina, silica and carbon-containing materials to a temperature of 1500-1600 ° 0 to produce silicon carbide and carbon monoxide. The mixture containing silicon carbide is heated to a temperature in the range of 1600 ° C to 1900 ° C, preferably 1700 ° C to 1900 ° C to produce alumina and carbon monoxide. The mixture containing silicon carbide and aluminum oxycarbide is then heated to 1950-2200 ° C to produce an aluminum silicon alloy. In this way, only the carbon monoxide formed during each reaction step passes through this and the previous reaction step, so that the metal product obtained can be maximized.

According to the process of the present invention, aluminum silicon alloys are prepared carbothermically from a mixture of carbon and alumina-silicon dioxide materials by reacting these materials in three steps. In the first step, the mixture is reacted at 1500-1600 ° C to produce silicon carbide and carbon monoxide. In the second step, the silicon carbide-containing mixture is heated to 1600 to 1900 G to produce alumina and carbon monoxide, and in the third step, the silicon carbide and the aluminum oxycarbide are heated to I95O to 2200 DEG to produce an aluminum-silicon alloy. In carrying out the reaction in this manner, carbon monoxide and other gaseous materials formed during the treatment at 1500-1600 ° C can be removed without passing through the materials resulting from subsequent treatment at elevated temperatures. Carbon monoxide or other gaseous products formed by treatment at 1600 to 1900 ° C may also be removed without passing through the alloy forming region. In this way, the alloy can be produced in substantially higher yields because the gaseous products do not pass quickly through the ranges corresponding to the alloy formation stages.

The ores containing alumina and silica include anorthosite, nepheline, dawaonite, bauxite, laterite and slate. Other sources of alumina include ash and coal waste. Said alumina containing and other attfags for use in the process of the present invention are summarized in the following table, where the typical composition range is given.

Table I

Aluminum Contains - Chemical Composition Range (% by Weight) Raw material • k o Γ * < SIÓ, Fe _a O, TIO, CaO MgO Well, 0 K, 0 anortozlt 16.1 to 32.72 from 45.78 to 60.7 0.15-9.90 0.02 to 3.21 5.0 to 18.72 0.02-6.43 0.68 to 7.1 0.03 to 8.1 (average) (25.72) (54.54) (033) (0.52) (9.62) (0.83) (4.66) (1.06) nefelln interval 12.4 to 27.10 38.35 to 60.03 1.54 to 8.64 0.40 to 2.6 036-19.94 0.22 - 5.99 3.72 to 9.72 0.25 to 9.54 (average) (21.30) (55.38) (2.42) (0.66) (1.98) (0.57) (834) (534) leucite interval 7.90 to 20.29 38.28 to 51.93 3.17-739 0.20-439 1.66-1236 032-1738 0.90 to 8.49 4.98-931 (average (16.05) (47.05) (3.49) (1.54) <1030> (6.20) (2.35) (5.38) aluminum-containing rock 17.58 to 29.45 0.22-6630 0.02-1037 0.05 to 3.80 0.05-0.26 0.01-1.0 0.16 to 4.72 0.71 to 10.46 rocks containing dewsonl 9.78 to 13.81 35.1 to 533 3.67-432 14.8 to 33.9 7.0 to 13.43 13-4.4 1.6 to 43 The aipo is a rock with ₄ contents 5.98 to 14.9 40.92 to 69.46 1.32 to 2.86 031 to 0.66 030 to 8.98 0.01 0.03-033 0,00- bauxlt 33.15 to 61.61 0.43 to 38.60 0.98-2830 0.67 to 4.08 0.00 to 8.7 0.00-034 0,00-0.16 0.00-034 laterlt 15.1 to 44.1 2.25 to 68.0 33 to 60.00 0.18 to 8.40 0.47-230 033 to 1.88 Bl-alumínlumoxld X slate 1130 to 39.50 46.60 to 78.63 0.67 to 6.74 030-033 0.10 to 8.90 034 to 3.62 0.11 to 1.92 2.21 to 5.0 szénzulladék ash 8.0 to 38.2 15.0 to 68.7 1.30-563 03-4.7 0.02 to 36.0 0.2 to 10.8 0.1 to 83 0.1 to 4.7 coal and lignite wind horse ash 2.2 to 36.3 43-087 13-363 036 to 1.09 234-4931 03-263 03-9.0 03 to 1.42

Among the substances listed, anorthosite, nepheline, leucite and dawolite contain significant amounts of CaO, MgO, Na 2 O and KpO. Anorthosite, which is a mixture of anorthite (CaOAlpO 2 S 10 O 4) and albit (NaAltil 2 O 2), is a preferred source of alumina for the process of the invention.

In order for the alumina-silica-containing material to be economically reduced by carbothermic processes and to produce the aluminum-silicon alloy in high yields, the weight ratio of the material to silica-alumina should be in the range of 0.151, preferably 0.7 to 1.0. A particularly preferred ratio is 0.9. The range of 0.7 to 1.0 is advantageous in some respects, while the ratio below 0.7 produces aluminum carbide, which reduces overall yield. Even at higher ratios, such as high silica content, the cost of the ore is advantageously reduced. domain. This is especially the case when the silica content is high while the alumina content is low in the ore. Thus, higher ratios of silica to alumina are economical. are much more advantageous. Higher yields result in higher yields ·

Low alumina materials are those which contain less than 35% by weight of alumina art apple, and in particular those with an alumina content of 8% to 35% by weight. Such low alumina materials generally have a silica content of 25 to 65% by weight.

In the case of low alumina materials such as anorthosite or low silica materials such as bauxite, the silica to alumina ratio may be adjusted to fall within the said preferred range. In the case where an anorthosite having a silica to alumina ratio of about 2.15 is used as the starting material, this ratio may be adjusted to the preferred range by adding an alum-rich ore, preferably low silica, or bauxite. . The bauxite used for such adjustment should preferably contain more than 35% by weight of alumina. Further, the bauxite may preferably contain from 40 to 55% by weight of alumina and from 0.1 to 15% by weight of silica. It is also advantageous if a significant amount of iron oxide is present in the adjustment material, _for example bauxite or the starting material. The iron oxide is preferably present in an amount of 0.5 to 50% by weight. The presence of iron oxide in the alloy is advantageous because it reduces the volatility of the alloy produced, which results in higher product yields. Alumina-rich purified materials, such as purified bauxite, can also be used, but are less advantageous because the material requires a separate cleaning step and costs, and yields are lower *

Another way to adjust the ratio to the appropriate range is to use silica physically. It is thus obtained by enrichment or washing. For example, alpha quartz, which represents a large amount of silicon dioxide in the anorthosite, can be obtained by treating the matrix with hydrogen fluoride. The hydrogen fluoride used to recover the silica can be 1-10% by weight * .The temperature of the washing solution is in the range of 60-100 ° C and the washing can be carried out for 1/2 to 3 hours. If hydrogen fluoride is used to wash the anortosite, the silica-alumina ratio

It can be reduced from 2.2 to 1.4 by washing with 10% w / w hydrogen fluoride at 100 ° C for one hour. In this way, the amount of alumina-rich ore required for the desired ratio can be significantly reduced #

The silica content of the slate or fly ash is reduced by washing with hydrogen fluoride to adjust the desired silica-alumina ratio. Higher ratios are very beneficial for silica washing *

In another method of adjusting the weight ratio of silica to alumina, silica is added. For example, when using bauxite in which the weight ratio of silica to alumina is in the range of 0.02 to 0.05 as the alumina-silica-containing material. you can add a source of silica to set the desired weight ratio *

Of course, the silicon dioxide to alumina weight ratio can be adjusted by combining these steps. For example, the ore is partially washed to remove silica and then bauxite is added to the partially washed ore to adjust its desired silica to alumina weight ratio.

In the case where the ore is prepared for the process according to the invention, it can be ground to a needle particle size of 1.17 mm to 0.074 mm, preferably 0.147 mm to 0.589 mm. The alumina-silica-containing material is preferably enriched or mechanically separated prior to adjusting the desired weight ratio, such as flotation, sedimentation, or magnetic separation. In the case where the ore used is, for example, anortosite, it is preferably treated with hydrochloric acid to remove calcium oxide (CaO), sodium oxide (Na 2 O) and the like. Effe may use 5-20% w / w hydrochloric acid and treatment is carried out at 60-100 °. Suitable treatment times range from 1/2 hour to 5 hours * After such treatment, the ore can be washed with water. This cleaning treatment may be combined with an acidic wash to remove the silica. ..........

For the purpose of reduction, a mixture of a carbonaceous material and a material containing silica and alumina in the desired gold may be used. Such a mixture may contain from 15 to 50% by weight of carbonaceous material, preferably from 19 to 28% by weight of carbonaceous material. * Carbon, preferably blast furnace coke is used as the carbonaceous material * as it is still perforated which is advantageous for reducing J * 0 a_ j O kiy) ÁX, τ

The mixture can be reduced in both a blast furnace and an electric furnace * Reduction in a blast furnace is more economical * A larger amount of carbonaceous material must be introduced into the blast furnace for reduction and heating purposes. Thus, in addition to the coal used, the reduction wood must be fed with 40 to 60% by weight of carbonaceous material for blast furnace heating.

If oil shale is used as the alumina-silica-containing material, volatile hydrocarbons are preferably recovered. The slate is silyl clum-alumina * oxide. prior to adjusting the weight ratio to obtain such materials. The treatment may include physical or chemical enrichment and carbonization to extract volatiles and to coke carbonaceous materials. Coke in the slate, as mentioned above, reduces the amount of reducing material to be ingested.

In accordance with the principles of the present invention, the process is controlled to provide aluminum-silicon alloys according to the following equations;

/ a / JSiO ₂ + 90 -> 5810 + 600 / b / 2A1 ₂ O ₅ + 50 —-> A1 ₄ O ₄ C + 200 / o / Al ₄ 0 ₄ C + 5SiC - *> 4A1 + 58 i + 400

That/. / b / and / c /, respectively reactions in 1500 - 2200 is carried out at 0 ° "C - 1600 ° C in a 1600 to 1900 C ^ö -one 1950th The process according to the invention is controlled in these temperature ranges. shall be carried out in such a way that the materials used in the production of aluminum-silicon alloys react in this order. For example, if the aluminum-silicon alloy is continuously produced in a furnace, the alumina, silicon dioxide and carbon introduced at the top of the furnace are heated to a temperature of 1500-1600 ° 0 to complete the reaction. Heating at this temperature is carried out in a zone adjacent to the top of the furnace. This heating zone allows carbon monoxide to escape without passing through the next and higher temperature zones. Thus, in the case where the reaction (a / b) is carried out, the carbon monoxide formed is also removed before passing through the alloying zone.

An important aspect of the process according to the invention is to minimize the possibility of carbon monoxide gas passing through the zones. In fact, allowing a large amount of gaseous material to pass through the production zones results in a very small amount of aluminum-silicon alloy because the gaseous material passing through the metal-producing zone would carry a large amount of the alloy formed.

The amount of carbon monoxide formed in the low temperature zone is half the amount of carbon monoxide produced in the furnace · In the intermediate temperature zone, carbon monoxide is formed at a tap rate of 1/6. In this way, 2/5 of the total carbon monoxide produced does not pass through the zone producing the aluminum-silicon alloy, which results in high yields.

If the volume of carbon monoxide gas formed from alumina-silicon dioxide material and carbon heated in the electric furnace at room temperature and in the range of '12100 ° C is measured by volume, then the measurements show that carbon monoxide evolution is at about 1580 ° C, that silicon arm? fold and carbon monoxide are formed according to reaction (a). The F (we found that the second peak * of carbon monoxide gas formation is at 178 ° C ^{D according} to a / b /) while the third peak occurs at about 2080 0, indicating the formation of the ajLuminium-silicon alloy ·

The temperature of the reactions in these; control in zones is intended not only to minimize the distraction effect of carbon monoxide gas formed during the reduction of alumina and silica. to reduce the effect of carbon monoxide from other sources, such as pollutant oxides in ore, such that ϊ'θ ₂ ° 3 » ^K 2 ⁰ '^ ^a 2 ^ * TiO ₂ , MgO and CaO can also be reduced to form carbon monoxide that it is very advantageous to remove the carbon monoxide before passing through the alloying zone.

Although it is desirable that the volatiles from the furnace be removed to such an extent that they do not come into contact with the aluminum-silicon alloy in the third step of production, a certain amount of volatile material may be used in the process. Thus, carbon monoxide from the reduction zone and the SiO, Al2O, Si and A1 vapor released during heating may serve to preheat the feedstock, after heating the feedstock to produce SiO, A1 _? O and A1 can be separated on the material to be fed and thus returned to the furnace. Thus, by minimizing the product suction effect of the sulfur monoxide gas passing through the alloying process, controlling the temperature of the reaction zones, and precipitating the volatiles on the material to be fed, aluminum-silicon-alumina-alumina-alumina-silicon alloy can be produced.

The heat input or reaction temperature in each zone can be controlled by the oxygen supplied when blast furnaces are used. The temperature of each zone can be controlled by the amount of oxygen that is introduced into each zone to burn carbon for heating. Thus, the amount of oxygen introduced into the low temperature zone (1500-1600 ° 0 °) determines the amount of carbon burned in the zone. The temperature in the next or hotter zone (1600 - 1900 0 °) can also be controlled by the amount of oxygen used to burn the coal. One of the important advantages of the process of the invention is the use of incomparably inexpensive material to produce the thermal energy required to carry out the reactions. Carrying out the reactions in the above order allows the preparation of aluminum-silicon alloys according to the principle of blast furnaces. In addition, by carrying out the reactions in the manner described, it is also possible to use air as an oxygen source in at least the first two reaction furnaces. If necessary, oxygen-enriched air may be used in the first two reaction zones ·

Due to the proper control of the previous reaction steps, relatively pure oxygen may be used in the third or hottest zone to burn the carbon introduced for heating without any appreciable loss of the metal product. The use of oxygen allows us to minimize the amount of gases from this step and also contributes to maximizing product yield. Of course, this zone can be electrically heated, either on the basis of the ivory or the de-stove furnace, to further reduce the amount of gas evolved there. _a ,

However, since electric heating is less economical, this method of heating is not preferred.

Another important aspect of the process according to the invention is that carbon can be added to the blast furnace. In a preferred embodiment, the heating coal is preferably introduced in the appropriate zone together with the oxygen source. The introduction of carbon in this way has the advantage that it also provides temperature control in each zone. In fact, knowing how to feed alumina-silica-containing material into the furnace! velocity, sufficient oxygen and carbon can be introduced into each zone to provide the necessary heat? to ensure a moderate temperature. A further advantage of this method is that the coal for heating purposes does not have to be transported through the previous zones.

The carbon to be added with the oxygen is preferably introduced in the form of coke, which is ground to a powder, since it becomes suitable for introduction into the zone by means of air or oxygen.

The advantage of initiating the reactions in this manner is that it is possible to feed portions in which the weight ratio of silicon oxide to alumina can be varied to a large extent compared to conventional operations. In the process according to the invention, the weight ratio of silica to alumina in the administered doses can be in the order of 0.2 to 0.5 without any adverse effects. These low weight ratios are extremely advantageous because weak bauxites, such as those with a high silica content, such as those containing, for example, 5% or more, can be used. As a result of the low weight ratios, the amount of silica to be added to such bauxites can be reduced.

Herein, the process according to the invention is a preferred embodiment. The following example is intended to provide a better understanding of the process of the present invention.

Example

1500 g 25% alumina and 55% silicon dioxide / 0.589 mm mesh / anorthosite, 557 g alumina / 0.147 mm mesh /, 454 g calcined petroleum coke and 452 g black coal / tar pitch / the briquettes are calcined at 1100 0. Aluminum oxide must be added to the anorthosil to adjust the weight ratio of silica to alumina to 0.89. Part of the briquette-coated mixture over a complete period, approx. Heat for 562 minutes in a graphite melting pot using a 50 kilowatt induction furnace. Heating should be carefully controlled, especially in the temperature range 1000-2150 0 °, and a definite temperature increase should be ensured. The temperature is monitored by means of an optical pyrometer, the volume of carbon monoxide gas released from the briquette mixture is measured by chromatography. After heating for 112 minutes, the amount of evolving carbon monoxide reaches a peak indicating that the reaction leading to the formation of azilium carbide and carbon monoxide. Gas evolution peaked at 1580 ° C.

Heating of the reaction mixture is continued and another peak of carbon monoxide evolution is observed after 276 minutes, indicating that the formation of alumina and carbon monoxide

176,191 resultant reactions (second stage of the process) were also performed. Ά The second peak of gas evolution occurs at 1780 ° C.

Continued heating of the reaction mixture, after 562 rounds, resulted in a new peak in carbon monoxide evolution, indicating that aluminum-silicon alloy formation and carbon monoxide development (the third step of the process of the invention) had also taken place.

For gas evolution, the third peak was observed at 2080 0 °. The experiment was evaluated after 562 minutes when the furnace was cooled and the product analyzed. It was found that 65 g of aluminum-silicon alloy were obtained.

In the preceding experiments, the same composition of briquettes was used and was, for example, ca. 1800 was heated to 0 ° C, no aluminum-silicon alloy could be produced, but instead a single powdered material consisting mainly of silicon carbide and aluminum oxycarbide was obtained. Similarly, it has been found that when heated to 1550 0 ° for a mixture of the same composition for comparison, a composition consisting mainly of silicon carbide, alumina and carbon was obtained. Similarly, it has been found that, if a mixture is heated to only 1400 ° C, for example, the resulting powdery material consists of carbon, silicon and alumina. Thus, it can be seen that in order to produce metal aluminum, the reaction must be carefully controlled in a manner consistent with the process of the invention.

Claims (10)

CLAIMS 1. A process for the carbothermic production of aluminum-silicon alloys from materials containing alumina and silicon dioxide by carboxylic reduction of these materials in the presence of a carbon source, characterized in that a material containing from 0.15 to 1.1% by weight of silica and alumina and heating a mixture of 15-50% carbon sources to 1500-1600 ° C to produce silicon carbide and carbon monoxide, heating the mixture containing silicon carbide to 1600-1900 ° C to form alumina and carbon monoxide. the silicon carbide and the aluminum oxycarbide are heated to 1950-220 ° C and the aluminum-silicon alloy is recovered, while the carbon monoxide formed during the heating to 1500-1600 ° C is removed without passing through the materials formed at 1600-1900 ° 1950 Carbon monoxide formed upon heating to 2200 ° C and from 1600 to 1900 ° C is also removed without passing through the alloy obtained from 1950 to 2200 ° C. 2. The process of claim 1, wherein the alumina and silica-containing materials are ground to a particle size of from 1 to 17 mm to 0.074 mm. . A method according to claim 1 or 2! way, characterized by the use of a mixture, 176,191, wherein the weight ratio of silicon dioxide to aluminum oxld is 0.7 to 1.0. The process according to any one of the preceding claims, characterized in that the material containing alumina and a silicon oxide is anortosite. The method of watering according to any one of the preceding claims, characterized in that the alumina and silica-containing materials are bauxite having an alumina content of at least $ 3% and silicon oxide in an art apple up to 15% by weight. 6. The process of claim 1, wherein the alumina and silica-containing material is an alumina-rich material having a silica content in the range of 0.1 to 15.0% by weight, and further silica is added. . Method of dispensing a process according to any one of the preceding claims, characterized in that materials containing silica and alumina containing from 0.5 to 50% by weight of iron oxide are used. A method according to any one of the preceding claims! way _? characterized in that the aluminum Sziliciumütvözetet prepared furnace in which the mixture comprising alumina, silica and a carbon source in the furnace 1500 - mixture comprising silicon carbide · a 1600 administered first zone ° 1600 C temperature, - fed to the second zone 1900 C ^ö temperature and transferring the silicon carbide and the aluminium oxycarbide to a third zone at a temperature of 1950 to 2200 ° C, while heating the at least the first and second zones with carbon source and oxygen from an oxygen source. 9. The process of claim 8, wherein the temperature required is achieved by using carbon in an amount of 40 to 60% by weight of the mixture fed to the furnace. 10. A process according to claim 8 or 9, wherein the oxygen source is air. 11. A process according to claim 8 or 9, wherein the oxygen source is pure oxygen. ...____________ 12th 8-11. A method according to any one of claims 1 to 3, characterized in that coal and oxygen are used for heating the first and second zones of the gas, the third zone being run on peAig electric current.